The present invention relates generally to a cryorefrigerator, and more particularly to a split-Stirling cryorefrigerator which can be tuned for efficient cooling over a range of operating conditions.
Cryorefrigerators (also known as cryocoolers) are used for low temperature cooling. Known cryorefrigerators include Stirling-cycle cryorefrigerators, such as split-Stirling cryorefrigerators. A split-Stirling cryorefrigerator is ordered from a manufacturer based on a required temperature and cooling capacity. In a typical split-Stirling cryorefrigerator, there is a helium gas source having a gas pressure which varies sinusoidally about a predetermined pressure. It is known that the amplitude of such sinusoidal pressure (i.e., the difference between the minimum and maximum pressure) helps determine the cooling capacity (expressed in Watts) of the cryorefrigerator. However, attempts at increasing the cooling capacity of a manufactured split-Stirling cryorefrigerator by increasing the amplitude of the sinusoidal pressure of the gas source led, paradoxically, to a decreased cooling capacity. In fact, in many such attempts, the cryorefrigerator completely stopped operating and had no cooling capacity at all!